Project Summary/Abstract In the past, medical tenets held that premature infants born ?late preterm? between 34 and 36 weeks have negligible neonatal complications with long term prospects essentially the same as those born at term (at 37 weeks or later). It is now recognized that late preterm infants are at increased risk for death and serious neonatal respiratory morbidity including respiratory distress syndrome and bronchopulmonary dysplasia, in addition to other adverse outcomes. Since three fourths of preterm births occur in the late preterm period, this is a significant public health problem. To address this issue, the NICHD Maternal-Fetal Medicine Units (MFMU) Network recently completed the Antenatal Late Preterm Steroids (ALPS) trial where women at risk for late preterm delivery were randomized to betamethasone, a therapy that is standard of care for improving neonatal respiratory and other outcome at earlier gestations, or placebo. The ALPS trial showed a significant decrease in neonatal respiratory morbidity. These notable findings will change practice in obstetrics, and understanding the long-term implications of this therapy is paramount. Moreover, little information on long-term pulmonary outcomes of children born in the late preterm period are published, and no statistics on the effects of antenatal betamathasone exposure in this population exists. These data are critical to understand the results of ALPS as well as to provide much needed information regarding childhood sequelae of late preterm birth. This application entitled ?Pulmonary Complications in a Birth Cohort after a Randomized Trial of Antenatal Corticosteroids: the ALPS Follow-Up Study? (ALPS-FS) describes a prospective follow-up of the ALPS trial to test the following hypotheses: 1) childhood chronic lung disease is lower in those exposed to betamethasone compared with placebo, 2) childhood chronic lung disease varies by gestational age at delivery from 34 to 40 weeks, and 3) various obstetric conditions such as preeclampsia and growth restriction are risk factors for childhood chronic lung disease, after accounting for gestational age at birth. Children whose mothers were enrolled in ALPS will have pulmonary function testing in addition to a comprehensive assessment of respiratory illness via questionnaire and medical records. Prospective respiratory symptomatology will be ascertained via text messaging for a period of one year. Children born to low risk women enrolled in a concurrent MFMU trial will serve as term controls.